Windows 7 has a cleanup routine that if more than 3 desktop icons are invalid due to missing program, not connected, or for other reasons, or some such, Win 7 deletes desktop icons to clean up. This seems to happen after Saturday night whenever the PC is
brought up, or just running. This is known ridiculous decision of Microsoft that they never fixed because Service Pack 2 never came out so they would not have to extend Windows 7 support expiration.
I had desktop icons missing, and did the hotfixes, and added the registry keys to prevent the two types of cleanup, and so did my friend, and all desktop icons remain now. See my previous posts in this and other threads about this. I have included one
below. This is a known crazy issue you can google and find whole articles about it. Good Luck!
The solution of turning off the diagnostic was outdated years ago by a hotfix and registry update (or fixits), to only stop the icon missing problem. Turning off a possibly major function, might not be the best for everyone.
See KB2642357, and be sure to run the hotfix at the top in blue box before running the fixits, or doing the registry updates. It will send an email with the link to the hotfox, but comments in other solutions give the link if you can't wait for the email.